DESCRIPTION: Studies on regeneration and retrograde transport in Aplysia neurons identified a set of retrogradely transported proteins which contain a nuclear import signal. This signal peptide sequence is homologous to the nuclear import sequences found in a variety of other proteins, such as the S40 large T-antigen and exogenous proteins with this sequence attached are subject to both retrograde transport and nuclear import when introduced into the axon. Proteins containing such sequences have now been obtained and identified in rat. These proteins are thought to represent prototypes for the elusive nerve injury signal which is thought to mediate the cell body response following nerve injury. The experiments in this application are intended to characterize endogenous proteins containing these sequences and their associated polypeptides.The biology of these proteins in Aplysia and rat nerve will be explored in the hopes of providing insights into the cell body response after nerve injury and identifying the underlying molecular mechanisms.